Automatic telephone system



Nov.,27,192s. I H 1,693,124

R. F. STEHLIK AUTOMATIC TELEPHONE SYSTEM Ori inal Filed May 192 2Shefis-Sheet 1 LAST TO OPEN l InUEnZur Ru :JUZFh F SZEHIK Nov. 27, 1928.

- R. F. STEHLIK AUTOMATIC TELEPHONE SYSTEM Original Filed May 29. 1924 2Sheets-Sheet 2 Inuzn :51" Tu duIFh F1 E'Iihhk M4 Patented Nov. 27, 1928.

UNITED STATES PATENT OFFICE.

RUDOLPH F. STEHLIK, OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESNEASSIGNMENTS, TO

AUTOMATIC ELECTRIC INC, OF CHICAGO, ILLINOIS, A CORPORATION OF DELA-WARE.

AUTOMATIC TELEPHONE SYSTEM.

Application filed May 29, 1924, Serial No 716,577. Renewed February 27,1928.

The present invention relates in general to automatic telephone systems,but is concerned more particularly with improved circuit arrangementsfor the automatic switches that are employed in telephone systems; andthe principal object is the production of new and improved circuitarrangements whereby automatic switches may operate with a better marginof safety and with less likelihood of failure when used in connectionwith lines having adverse characteristics as regards their use incontrolling automatic switches.

It is a further object of the invention to simplify, as much aspossible, the circuits of the automatic switches in order to permit thecontrolling relays to be made with a smaller number of springs so as tofacilitate their operation and to permit a more ready response to thecurrents sent through their windings.

.There are various other objects, having to do mainly with the circuitdetails necessary for carrying out the objects set forth above. Theselatter objects, together with the previously mentioned ones, will bereadily understood from a further perusal of the specification.

Attention is directed to my co-pending application, Serial No. 582,333,filed August 17 1922, on which the present case may be considered animprovement.

Referring now to the accom Janying drawings comprising Figs. 1 and 2,they show by means of the usual circuit diagrams a sufii cient amount ofequipment employed in an automatic telephone system embodying theprinciples of the invention to enable the invention to be understood andits utility appreciated.

Fig. 1. shows the substation A and the associated line which terminatesat. the exchange in the line switch LS, together with the selector Swhich is accessible to the line switch LS; and Fig: 2 shows theconnector C which is accessible to the selector S, Fig. 1, and which hasaccess to the line of substation B with which there is associated theline switch LS. V

The substations A and B are of the usual automatic type; the lineswitches LS and LS are of the well known rotary type, mechanically, andtheir wipers have no normal position and are moved in a forwarddirection only; and the selectors S, together with the connector C, ismechanically of the well known vertical and rotary type of switch.Accordingly, its bank contacts are arranged inhorizontal rows or levels.

In the drawings the relays that are slow acting have been indicated intwo ways. Gertain of these relays have copper collars around thearmature ends of their cores. Such copper collars are indicated bymaking the upper section of the core solid black, the upper end of therelay being assumed to be the armature end. Other relays have coppersleeves or tubes around the full length of the iron cores. Such relayshave been indicated in the conventional manner by drawing two extralines through the core to indicate the thickness of the copper sleeve.Among such relays may be mentioned the relays 104, Fig. 2, and the relay105, which latter relay has both a copper sleeve around the core and acopper collar upon the armature end of the core.

The apparatus, having been described generally, will now be describedmore in detail, and for this purpose it will be assumed that thesubscriber at substation -A, desiring to converse with the subscriber atsubstation B, removes his receiver.

\Vhen the receiver is removed at substation A, a. circuit is closed overline conductors 11 and 12 for the line relay 15 of the line switch LS.Line relay-15 thereupon energizes and places ground upon private normalconductor 13 at armature 19, thereby making the calling line busy to theconnectors having access to it and closing a circuit for the switchingrelay 14 and stepping magnet 21 in series. Line relay 15 also connectstest wiper 23 to the junction of switchingrelay 14 and stepping magnet21 at-armature 20. Assuming, however, that the trunk upon which thewipers of the line switch are standing is idle, this latter operationdoes not have any particular utility at. his time and switching relay 14energizes immediately, but, on the other hand, assun'iing that the saidtrunk is busy, the test conductor thereof is grounded and the groundpotential is applied through test Wiper 23, armature 17 and its restingcontact, and armature 20 and its working contact to the junction ofrelay 14 and magnet 21, short circuiting relay 14 and preventing it fromener- 1a energizes in series with stepping magnet.

21, but stepping magnet 21 does not energize at this time on account ofthe high resistance of switching relay 14; Upon energizing, switchingrelay 1% disconnects the line conductors 11 and 12 from the winning ofline relay 15 and ground and extends them by way of wipers and 24:,conductors 25 and 27, and armatures 5'7 and 60 to the upper and lowerwindings, respectively, of line relay of the selector Line relay 35 nowenergizes over the calling line and at armature 51 removes the shortcircuit normally around relay 36 and closes a circuit for the relay 36as follows: from round by way oi the restin L) .1 :1

contact and armature 59 of relay 39, release relay 36, working contactand armature 51, series relay 37, and vertical magnet to battery.Release relay 36 energizes over this circuit, but vertical .inagnet 40and series relay 37 are not operatively energized on account oi the highresistance of release relay 36. It is true that, while the threecontacts of line relay 35 are all together, a circuit is closed forrelay 37 and magnet 40 independent of the normally short circuitedrelease relay 36, but this condition exists for such an extremely shorttime that relay 37 and magnet i-O do not have time to operate beforerelay 36 is cut into the circuit.

Relay 36, upon energizing responsive to the above closure of itscircuit, opens a point 1n the circuitof release magnet 41 and closes alocking circuit for itself at armature 53, independent oi? armature 51and its working contact, and armature 52 places ground upon releasetrunk conductor 26 thereby closing the usual holding circuit throughwiper 23 and armature 17 its working contact for SWitChiDg' relay 1 ofthe line switch LS beiforethe slow acting line relay 15 has hadtime toiall back. v

-The' above operations have all taken place responsive to the removal ofhe receiver at thecalling substation, and the circuits are now inreadiness for the first cgit in the desired number to be d1 alled. Vihen the sub 'scriber substation I; manipulateshis calling device inaccordance with the first digit in the desired number, the circuit ofline relay number of times.

35 of the selector S is opened'a corresponding Line relay 35 deenergizeseach time its circuit is opened and at the nor mally closed contacts ofarmature 51 replaces which and through the interrupter contac s theshort circuit around the release relay 3 whereupon vertical magnet L0and series lay 37 energize over'the'following circuit from ground by wayof the resting contac and armature 59, normally closed contactcontrolled by armature 51,'armature and its working contact, seriesrelay 37, and vertical magnet $0 to battery. Pelay on remains energizedthrough the series of deenergizations of relay 35 because the currentcontinues to flow through its short circuited winding for a time afterit is removed from the main circuit, maintaining the relay energized inthe well understood manner. By the operation of vertical magnet i0,which energizes each time relay 36 is short ci*- cuited, the wipers6163, inclusive, of the selector are raised step by step and come torest opposite the desired level of bank contacts. Relay 37is energizedin se"ies with vertical magnet 4-0 and, being slow acting, maintains itsarmature attracted throughout the vertical movement. As soon as the ofinormal contacts at are closed upon the first vertical step of theswitch, a circuit is closed from the grounded release trunk conductor 26through the working contact and armature 54;, and the on normal contactsfor stepping relay o8. Relay 38, thereupon energizes; prepares circuitfor rotary magnet 2 at armature 55; and at armature 56 closes a lockingcircuit for itseli which includes the resting contact and armature 59and the interrupter contacts 45.

At the end of the vertical movement, the relay 37 falls back andcompletes the circuit of rotarymagnet 42st the normally closed contactscontrolledby armature 54. Rotary magnet 12 thereupon energizes througharma ture 55 and its working contact and advances wipers 6163,inclusive, into engagement with the first set of bank contacts in'theselected level, and, near the end or its stroke, opens the lockingcircuit of stepping relay 38 at interrupter contacts 15. l hen'thisoccurs, stepping relay 33 deenergizes and opens the circuit of rotarymagnet as at armature 55, whereupon rotary magnet 12 deenergizes alsoand closes its interrupter contacts again. The further operation dependspen whether the-trunk terminating in the iii-st set of bank contacts isbusy or idle. idle, switching relay 39 energizes diate-ly, seizing thetrunlr. Assum trunk to be busy, ,iowever, switch 39 is short circuitedby the ground encountered on the busy test contact by tes wiper 62 anddoes not energize. i-rlso, etc i ping relay 33 energizes throughtest wiimmeit i ,s lilac.

n) potentia i and again closes the rotary magnet circuit at armature 55,at the same time again crosiug its locking circuit at armature 56. dlhenthis occursrotary magnet {i2 energizes and advances the wipers of theselectorinte 1, LHU

If it is engagement with the next set of bank contacts.

This alternate operation of stepping relay 38 and rotary magnet 42continues as described until an idle trunk is reached, which trunk, itwill be assumed, is the one comprising conductors 64-66, inclusive.WVhen this idle trunk is reached, switching relay 39, being no longershort circuited, energizes in series with stepping relay 38 through theinterrupter contacts 45 and on normal contacts 44, and from the groundedrelease trunk conductor 26. Stepping relay 38, however, does notenergize at this time on account of the high resistance of switchingrelay 39. Switching relay 39, upon energizing, disconnects conductors 25and 27 from the windings of line relay 35 at armatures 57 and 60. T ieadjustment of the relay is such that these armatures 57 and 60 areoperated immediately and break away from their back contacts anappreciable length of time before armature 59, which is the last tooperate, breaks away from its resting contact. Responsive to line relay35 being disconnected at armatures 57 and 60, the said line relaydeenergizes immediately, on account of the fact that it is an impulserelay and has a very accurate adjustment, and again short circuits therelease relay 36 so as to make it slow acting to permit it to hold upduring the switching period, thereby closing the usual circuit forseries relay 37 and vertical magnet 40. However, before the said relay37 and magnet 40 can operate, armature 59 of switching relay 39 breaksaway from its resting contact, thereby opening the circuit of relay 37and vertical magnet 40. To complete the descriptionrof the operation ofrelay 39 it may be stated that armature 58 opens the testing circuit andprepares the holding circuit, and armatures 57 and 60 extend the lineconductors 25 and 27 through wipers 61 and 6". the bank contacts uponwhich they are standing, conductors 64 and 66, and the normally closedcontacts controlled by armatures 122 and'122 to the upper and lowerwindings, respectively, of the line relay 102 of the connector C. Linerelay 102, upon energizing, closes at armature 124 a cir cuit for thenormally short circuited release relay 103, at the same time removingthe normal short circuit from around release relay 103. The circuit ofrelease relay 103 at llllS time is as follows: from ground by way ofrelay 103, working contact and armature 124, contact of off normalspring 113 and said spring, series relay 104, and vertical magnet 109 tobattery. Owing to the high resistance of relay 103 neither relay 104 normagnet 109 is operatively energized at this time. It is true that, afterarmature 124 engages its working contact and before the normally closedcontacts controlled by armature' open. a circuit is closed momentarilyrelay 104 and rotary magnet 109, independent of relay 103. However, thiscondition exists for such an extremely short time that neither relay 104nor magnet 109 has time to operate. Upon energizing, relay 103 opens apoint in the circuit of release magnet 3 and closes a locking circuitfor itself at armature 127; grounds the local locking conductor 152 atarmature 126; and at armature 125places ground upon the release trunkconductor 65, thereby closing a holding circuit which includes testwiper 62 and armature 58 and its working contact of the selector S forswitching relay 39 of the selector S and switching relay 14 of the lineswitch LS before the slow acting relay 36 of the selector S has had timeto deenergize.

lVhen the calling subscriber maniaulates his calling device inaccordance with tie second digit in the desired number, line relay 102of the connector C deenergizes a corresponding number of times and uponeach deenergization, closes at the normally closed contacts controlledby armature 124 a circuit for vertical magnet 109, the circuit at thetime of the first closure being as follows: from ground by way of thenormally closed contacts controlled by armature 124, armature 127 andits working'contact, contact of off normal spring 113 and said spring,relay 104, and vertical magnet 109 to battery. By the operation ofvertical magnet 109 the wipers 144-146, inclusive, of the connector, areraised step by step and come to rest opposite the desired level of bankcontacts. Relay 104 is energized in series with vertical magnet 109 and,being slow acting, maintains its armature attracted throughout thevertical movement. Relay 104 maintains its own circuit and that ofvertical magnet 109 intactat armature 128 after the off normal springshave shifted as they do upon the first vertical step. At the end of thevertical movement, relay 104 deenergizes and shifts the impulse circuitfrom the vertical magnet to the rotary magnet.

- The calling subscriber now manipulates his calling device inaccordance with the third digit of the desired number, whereupon linerelay 102 deenergizes a. corresponding number of times and, upon eachdeenergization, closes a circuit for rotary magnet 111 as follows: fromground by way of the normally closed contacts controlled by armature124, armature 127 and its working contact, normally open contact-scontrolled by ofi' normal spring 113, normally closed cont-actscontrolled by armat-ure 128, armature 142 and its resting contact, androtary magnet 111 to battery. By the operation of rotary magnet 111 thewipers of the connector are rotated step by step into engagement withthe bank contacts 147449, inclusive, of the line of substation B. Relay107 is energized in multiple with rotary magnet 111 and, being slowacting, maintains its armature attracted iao throughout the rotarymovement. Upon energizing, relay 107 disconnects testwiper 145 1'rom thelower winding of switching relay 108 and connects it instead to busyrelay 106 through armature 140 and its resting con tact. Relay 107 alsoplaces a shunt around armature 134 and its resting contact at armature137 so as to maintain its own circuit intact in case busy relay 106energizes during the rotary movement dueto test 'wiper 145 passing overbusy test contacts.

At the end of the rotary movement relay 107 deenergizes. Assuming thatthe called line is busy, thevbusy relay 106 is energized from ground onthe busy test contact en gaged by wiper 145, and at the time that relay107 deenergizes, becomes locked up over the following circuit: fromground by way of grounded release trunk conductor 65, armature 133 andits working contact, normally closed contacts controlled by armature136, armature 140 and its rest-ing cont-act, and

busy relay 106 tovba-ttery. With busy relay 106 energized and with relay107 deenergized, the said relay 10'. is disconnected from the operatinglead at armature 134 so as to pre vent it from energizing again toretest the line and open the locking circuit of busy relay 106 in casethe calling subscriber again manipulates his calling device. However, itis not necessary to disconnect the rotary mag net 111 because, eventhough a further op eration of the calling subscribers calling deviceresults in the further operation of rotary magnet 111, no harm canresult because busy relay 106 remains locked up and switching relay' 108cannot energize even though the wipers are rotated into engagement withan idle line. Busy relay 106 also connects the common busy signallingconductor to the lower heavy talking conductor at armature 135 so as totransmit a busy tone back to the callin subscriber. Upon hearing thistone after his calling device has come torest the calling subscriberknows that the called line is. for the time being, inaccessible, and hereplaces his receiver, resulting in the switches being released in amanner to be described hereinafter. It will now be assumed that the lineot substation B is idle when called. In this case, busy relay 106' isnot energized when the wipers of the connector come to rest upon thebank contacts of the called line, and relay 107, upon deenergizing atthe end of the rotary movement, closes a. circuit through the lowerwinding of switching rel 108 as follows: from ground by way of thegrounded release trunk conductor 65, armature 133 and its restingcontact, armature 181 and its resting contact, lower winding of relay108, resting contact and armature 136, test wiper'145, test contact 148,switching relay 150 of the line switch LS, and stepping magnet 151 tobattery. Relay 150 energizes over this circuit, but stepping magnet 151is unable to energize due to the high resistance of switching relay 150.Relay 150, on the other hand, is able to energize only part way onaccount of the usual inter-locking device (not shown) between itsarmature and that of the associat ed line relay. Accordingly, relay 150opens all its back contacts but does not close any of its frontcontacts.

In the connector C, switching relay 108 energizes over the above tracedcircuit; closes a locking circuit for its upper winding at armature 141;disconnects busy relay 106 at armature 140; directly grounds test wiper145 at armature 139; and at armat-rnres 138 and 143 connects up thewipers 144 and at the same time connecting up the small ring backcondenser 114 at armature 138. Relay 108 also disconnects the operatingconductor from rotary magnet 111 at armature 14:2 so as to prevent thewipers from being rotated further in case the calling subscriber againmanipulates his calling device. thereby removing rotary magnet 111 fromin shunt of relay 107. Ordinarily this would permit relay 107 toenergize in series with release relay 103, but in order to prevent thisarena ture 142 connects the operating lead ts vertical magnet 109.Accordingly, it the calling device is turned again vertical magnet 109will be energized, but, since the shaft carrying the wipershasbeenrotated, the stationary dog is in between two of the teeth on theshaft, thus mechanically preventing any further vertical motion of theshaft, even though the vertical magnet 109 energizes.

Ringing current is now intermittently applied to the called line throughthe upper winding of ring cut-oil relay 105 and over wiper 146 tooperate the. bridged. bell at the called substation, and returns overthe other side of the line and wiper 148 to ground through armature 132and its resting contact. The small condenser 114 which is connected upat armature 138 permits a sufficient amount of ringing current to leakback to the upper heavy talking conductor to inform the callingsubscriber that ringing current is being applied intermittently to thecalled line.

When the subscribed at substation B responds to the ringing of his bellby removing his receiver, a direct current bridge i s closed across theconductors of his line, where pon ring cut-oil relay 105 energizesthrough its upper winding; closes a locking circuit for its lowerwinding at armature 130; switches the back contact of armature 133 fromthe lower terminal of the lower winding of relay 108 to the upperterminal of the said winding at armature 131 for a purpose to beexplained fully hereinafter; and at armatures 129 and 132 disconnectsthe wipers 144 an d.146 from the ringing current'source and from groundrespectively and extends them to the upper and lower windings of thedouble wound back bridg relay 101. Relay 101, upon energizing, reversesthe current flow in conductors 6-1 and 66 at armatures 122 and 122. Thisreversal does not have any particular utility in connection with theequipment shown, but, asis well known, may be used when desired tooperate meters and the like. Relay 101 also places a multiple groundupon the local locking conductor 152 at armature 121, and at armature 123 opens a further point in the circuit of release magnet 110 for apurpose to be described hereinafter. The calling and called subscribersmay now converse with eachother as desired.

lVhen the conversation is terminated, the two subscribers replace theirreceivers. When the receiver is replaced at substation B, back bridgerelay 101 tie-energizes and reverses the current flow in the callingloop to normal, at the same time removing the multiple ground from thelocking conductor 152 at armature 121, and closes at armature 123 apoint in the circuit of release magnet 110.

Assuming now hat the calling subscriber does not hang up his receiverimmediately, the circuits remain as they are untilhe does replace hisreceiver. When his receiver is finally replaced at substation A, linerelay 102 of the connector C decnergizes and short circuits releaserelay 103 at the normally closed contacts controlled by armature 12 1,grounding the iinpinse conductor, which results in a circuit beingclosed over the impulse lead and through armature 142 of switching relay10S and its working contact for vertical magnet 109. Vertical magnet 109thereupon energizes but its energization does not have any particularutility at this time. Relay 107 is energized at this time in multiplewith vertical magnet 109 but does not produce any particular result atthis time. The slow acting release relay 103 deenergizes after theinterval for which it is adjusted; removes ground from the lockingconductor 152 at armature 126, whereupon relays 105 and 108 deenergize;removes ground from the impulse conductor and closes the release magnetcircuit at armature 127; and at armature 125 removes ground from therelease trunk conductor 65. Release magnet 110 now energizes over thefollowing circuit: from ground by way of the normally closed contactscontrolled by armature 124C, armature 127 and its resting contact,armature 123 and its resting contact, oft normal contacts 112, andrelease magnet 110 to battery. Upon energizing, release magnet 110restores the wipers 14 l1 l6, inclusive, of the connector C to normal inthe usual manner, whereupon the circuit of release magnet 110 is openedat off normal contacts 112.

.Responsive to the removal of the ground potential from the releasetrunk conductor 65, switching relay 14 of the line switch LS andswitching relay 39 of the selector S deenergize. Upon thedeenergizationof switching relay 39, a circuit is closed at contacts 59for release magnet 41 which includes the normally closed contactscontrolled by armature -51, armature 53 and its resting'contact, and offnormal contacts 43. Accordingly, theselector S is restored to normal inthe usual manner. The entire connection is released and the apparatusused therein is in readiness to be used again.

It will now be assumed that the subscriber at substation B does notreplace his receiver immediately upon the termination of theconversation, as hereinbefore assumed, but leaves his receiver oil thehook for a time. In that case, when the subscriber at substation Areplaces his receiver, line relay 102 falls back,

as 'hereinbefore described, resulting in a circuit being closed forvertical magnet 109 and relay 107 in multiple, whereupon relay 107energizes and disconnects the grounded test wiper 145 from the releasetrunk conductor 65 at armature 136 so as to permit relay 103 to removeground from release trunk conductor 65 prior to'the deenergization ofrelays 105 and 108. In this case, when release relay 103 deenergizes itremoves ground from the release trunk conductor 65 at armature 125,permitting the selector S to be released in the hereinbefore describedmanner, but the local locking conductor 152' is maintained,

grounded at armature 121 of the back bridge relay 101 and the circuit ofrelease magnet 110 is maintained open at armature 123.

Responsive to the removal of ground from the operating conductor uponthe deenergization of release relay 103, the slow acting relay 107 fallsback after the interval for which it is adjusted and replaces groundupon the re lease trunk conductor 65 at armature 136', the groundpotential now being applied to release trunk conductor 65 at armature139 and through armature 136 and its resting contact, working contactand armature 131, and the resting contact and armature 133. Accordingly,the connector C is guarded against seizure for the time being.

It will be noted that the lower winding of relay 108 is not merely shortcircuit-ed in order to get the ground potential by this winding, but itscircuit is opened so as to prevent the winding from being shortcircuited and thereby giving the relay additional slowness when itscircuit is opened upon the'release of the connection. Other wise, thewipers might remain connected up during the releasing movement, withconsequent annoyance to subscribers conversing on the lines over whichthe wipers pass.

Assuming now that the subscriber-at substation B replaces his receiver,back bridge relay 101 deenergizes and closes the release magnet circuitat armature 123, at the same time removing ground from the local lockingconductor 152 at armature 121. Responsive to the removal of ground fromconductor 152, relays 105 and 108 deenergize and relay 108 removesground from the release trunk conductor 65, thereby rendering the switchidle. Responsive to the closure of the release magnet circuit atarmature 123 of relay 101, the wipers of the switch are restored tonormal in the usual manner.

- Certain points in connection with the operation of the selector S andthe connetor C will now be considered more in detail and attention willbe directed toward the novel means employed for obtaining the desiredresults. Considering first the circuit involving relays 36 and 37 andvertical magnet 40 of the selector S, the contacts of line relay 85through which the vertical magnet 40 is operated are of themake-before-break type. The contacts arearranged in this manner in orderto insure that the vertical magnet a0 is left in the circuit for amaximum length of time, i. e., its circuit is closed almost as soon asthe armature of relay 35 starts to fall back 7 and remains closed untilthe armature h as almost completed its forward stroke again. Thisinsures that the magnet will get sufficient current to respond on a verymomentary .deenergization of the line relay 35. -Also,

since the circuit of vertical magnet- 40 is not opened by the armaturespring 51 directly, the liability of intense sparking (at the. contactscontrolling the vertical magnet circuit) upon the back stroke of thearmature of line relay 35 is entirely removed, owing to the fact thatthe armature spring ol'takes up the rebound of'the armature proper ofthe relay (not shown) and does not permit the armature proper of therelay to rebound far enough to again open the vertical magnet circuitwhile the relay 35 is deenergized. This undesirable result is often'encountered when the circuit of the vertical magnet is closed through anarmature spring and a cooperating back contact, but, as pointed outabove, is not found with the present arrangement.

Another novel result is obtained by the present circuit arrangementwhich is not found in prior circuit arrangements of this general nature.It has been commonly recognized for some time that a make-beforebreak sJTlII combination for controllin the operating magnet circuit of aselector or other switch is superior to the ordinary spring c mbinationfor reasons pointed out hereinbefore. However, the circuits using themakebefore-break spring combination heretofore have been open to theobjection that, if a calling line becomes leaky or defective to such anextent that a connection is extended through to a first selector, butthe leaky cond1t1on exists only enough to operate the line relay of theselector far enough to close the make contacts of the spring combinationbut not sufficiently to open the break contacts, the'release relayenergizes and closes a circuit for the vertical magnet, causing thevertical magnet to overheat and become seriously damaged or ruined in acomparatively short time. In the present case, however, the circuitarrangement is such that the release lay 36 does not energize if thearmature spring 51 is brought into engagement with its contact but isnot moved far enough to open the normally closed contacts. It is truethat a circuit is closed for vertical magnet l0 at such a time, butsince release relay 36 is not energized, no holding circuit is providedfor the seized line switch, which promptly releases, freeing theselector. Of course, if the condition still exists on the line introuble, the line switch operates again and again seizes the selector,and the same operation is repeated over and over until the trouble iscleared up. The vertical magnet 40 is energized momentarily each timethe selector is seized. However, the design of the vertical magnet issuch that it can withstand an indefinite series of momentaryenergizations without becoming dangerously hot. 7

Considering now the series relay 37, it will be noted that this relayismade slow acting by means of a copper sleeve which covers the coreover its entire length. This method of making the relay slow acting hasbeen chosen in order to insure that the relay will energize and remainenergized throughout a seriesof extremely short impulses. Owing to thefact that the copper sleeve extends over the entire winding spaceprovided on the core, all lines of force traversing the core must passthrough the copper sleeve and are then effective in maintaining thearmature of the relay attracted after the circuit of the re lay isopened. Of course, the usual copper collar placed on one, end. or theother of the relay could be used in this case, but, when, a coppercollar is placed upon a relay, it tends to prevent a quick building upof magnetic flux in the portion of the core covered by the copper collarwith the result that the lines of force in the remaining portion of thecore bypass the portion of the core covered by the copper collar throughthe air when the relay is first energized, and the building up of thelines of force through the copper col lar is a gradual process,relatively speaking,

and is forced only by the magnetic reluctance the cop-per sleeve whichwill be eifective in maintaining the armature of the relay at tractedafter the circuit is opened.

f further point in connection with the op- Ill) V circuit 'emainsesrablishec through relay The principal oration of relay 37 is that theamount of slowness imparted to the relay by the cop per sleeve does notneed to be as great as it does in the ordinary ci 'cuit owing to thetart that when relay 35 cuts the release relay in the circuit uponenergizing, a high resists having a tendency to enable the armature beattracted for a. short interval. In fact, this tendency is so markedthat when the selector is sed in connection with lines haying a hiresistance, the copper sleeve may be ntcd and relay 37 will operate aplain relay, because, on long lines, line relay 35 does not become sostrongly energized and fails lr-acl: quickly and remains back longer,with the consequent result that relay 35 does not rema energized so longbetween the suc essive deenergizations, and release relay 36 is cut intothe impulsing circuit for a shorter period of time.

llci now to the magnet operating cuit of cenns C, it will be noted thathis circuit id ntical with that of the selector S as regards t 1 'ngcombinations of 1 and release 102 and i023, respeeti once is that inentsare made tching the ope-racing circ i from the ver: al magnet to therotary mag net, as has described hereinheiore, the series relay itperating in identically the same n'iauncr a, he correspon'ch relay theselecte and the relay 107 operating in a similar ma zcept that it is inmultiple with tne associated ma 'net ill i stead of in series.

What is cla ed 1s 1. in a te one system, a connector switch having W11 atest conductor for said switch, a relay for connecting said wipers tosaid switch, a. winding on said relay, circult connections controlled bysaid relay for grounding said test conductor through said winding, acircuit for applying ringing current to a wiper of said connector, asecond relay for op ning said ringing circuit, and contacts on saidsecond relay for connecting the ground otential to said test conductorover a path independent of said winding and for removing said windingfrom the circuit.

ling combination comprising a line relay, a

,ase relay, and an operating magnet, norly open contacts on said linerelay for enizing said'rclease relay when said line relay operatenormally closed contacts on said line relay i [r encr izing said magnetwhen the line relay restores, all said contacts oeing closed when theilll'lltltlllC said line relay is in mid-p0 "n and circuit arrangementsfor shunting s release relay when all said contacts are eiosed,

itching device having motion in err us. a magnet for operating said edirection, a second magnet .ior ng said device in the other direction, a5 connected i ice with said first magnet when said de\ l operated insaid one direction, means for connecting said relay in peration of saiddevice in said one nd means for disconnecting said from said secondmagnet and for reaid relay in series with said first 5 'pletien of theoperation of other direction.

circuit having two branches extemling to secondary operating magnet, anda eh relay respectively, and means 10 mg each branch independent ot l.1* Lu Order 7. In a telephone system, an automatic switch, drivinmagnet, a subscrihers line accessibleto said s *itch, means foroperating said switch, to connect with said line, a relay in saidswitch, means for operating said relay and said magnet in parallel,means for testin 2 said line for the busy or idle condition,

d leans controlled by said testing means sconnecting said relayindependent of said magnet when said line is found busy.

8. In a two-motion connector switch, an impulse circuit having twobranches extending to the secondary operating magnet and a change-overrelay, respectively, means responsive to the switch being operated toconnect with a busy line for opening the changeover relay branch withoutopening the other branch, and means for disconnecting said magnetindependent of said relay when said line is found idle.

9. In an automatic switch, a line relay, a release relay, an operatingmagnet, a makebet'ore-brak spring combination on said line relay forcontrolling said release relay and said magnet, and a circuitarrangement such that the release relay is prevented from energizing incase the line relay is partially wi said second magnet at the compleenergized so as to close the make contacts without opening the breakcontacts.

10. In an automatic switch, a line relay, a release relay, an operatingmagnet, a makebefore-break spring combination on said line relay forcontrolling said release relay and said magnet, the make contactscontrolling said relay and the break springs con trolling said magnet,and circuit arrangements controlled by said release relay forautomatically releasing the said switch in case the line relay isoperated for enough to operate the make contacts but not far enough tooperate the break contacts.

11. In an automatic switch, .a line relay, a release relay, an operatingmagnet, a makebefore-break spring combination on said line relay forcontrolling said release relay and said magnet, and circuits suchthat anincomplete operation of said spring combina tion will cause the releaseof the switch and thus prevent overheating of said magnet.

12. In an automatic switch, an impulse responding relay, an operatingmagnet, a release relay which is rendered slow to release by being shortcircuited by normally closed contactsjcontrolled by the'impulsing relay,and a change-over relay which is rendered slow to release by separateand distinct means suchas a copper sleeve, said change-over r lay beingoperated in series with said magnet. 13. In a telephone system, aconnect r, a release conductor for the connector, a switching relay insaid connector, a winding for said relay, means for energizing saidwinding over a circuit including said conductor, a ring cut-oil relay insaid connector, and means controlled by said ring cut-ofi relay and saidswitching relay jointly for applying a characteristic potential to saidconductor over a path independent and exclusive of said winding.

14;. In a telephone system, a connector, a release conductor for theconnector, a switching relay having a winding one terminal of which isnormally connected. to said conductor, means for energizing said windingto operate said relay, contacts on said relay for grounding the otherterminal of said winding, a ring cut-oft relay in said connector, andmeans controlled by said ring cut-off relay for disconnecting saidconductor from one terminal of said Winding and connecting it to theother terminal of said wind- 15. Ina telephone system, a switch, a firstand a'second magnet, means for successively operating said magnets toposition said switch, a release relay for maintaining said switch inposition, and means for energizing said relay in series with saidmagnets successively.

16. In a telephone system, a switch, a first and a second magnet forcontrolling the oporation of said switch, a release relay in saidswitch, and means for energizing said relay in series with one of saidmagnets during the operation of the switch, and in series with the otherof said magnets at the completion of the operation of the switch.

In witness whereof, I hereunto subscribe my name this 23d day of May, A.D. 1924.

RUDOLPH F. STEHLIK.

